If benefits aren't graduated, then you can have a hypothetical situation where you can earn $25,000, and receive $5,000 of benefits, or earn $25,001 and receive $0 of benefits. In this hypothetical situation, every dollar you earn between $25,000 and $30,000 is extra work you have to do that doesn't net you any additional dollars.

There's a whole separate discussion to be had about what taxes should pay for, but I don't think it's abusing the system. I think there's no question the bartender would work full time at a job that paid enough to pay for all of the living expenses and the healthcare, but that's not one of her options. Her options, according to the anecdote, were to work X hours for X money, or to work X + Y hours for X money.